Articular cartilage is a type of hyaline cartilage that lines the surfaces of the opposing bones in a diarthrodial joint (e.g. knee, hip, shoulder, etc.). Articular cartilage provides a near-frictionless articulation between the bones, while also functioning to absorb and transmit the compressive and shear forces encountered in the joint. Further, since the tissue associated with articular cartilage is aneural, these load absorbing and transmitting functions occur in a painless fashion in a healthy joint.
Fibrocartilage is found in diarthrodial joints, symphyseal joints, intervertebral discs, articular discs, as inclusions in certain tendons that wrap around a pulley, and at insertion sites of ligaments and tendons into bone. Made of a mixture of collagen type I and type II fibers, fibrocartilage can also be damaged, causing pain in the affected joint. It is understood for purposes of this application that the term “cartilage” includes articular cartilage and fibrocartilage.
When cartilage tissue is no longer healthy it can cause debilitating pain in the joint. For example, articular cartilage health can be affected by disease, aging, or trauma, all of which primarily involve a breakdown of the matrix consisting of a dense network of proteoglycan aggregates, collagen fibers, and other smaller matrix proteins. Tissue cells are unable to induce an adequate healing response because they are unable to migrate, being enclosed in lacunae surrounded by a dense matrix. Further, since the tissue is avascular, initiation of healing by circulating cells is limited. Similarly, damage or degeneration of knee fibrocartilage i.e. the menisci, is a common occurrence. A damaged or degenerated meniscus has little ability to heal or repair itself because the pathology frequently occurs in the avascular part of the tissue.
Several articular cartilage repair strategies have been attempted in the past. These include surgical techniques such as microfracturing or performing abrasion arthroplasty on the bone bed to gain vascular access, and hence, stimulate extrinsic repair in the defective region. The long-term outcome of these techniques, however, has been known to result in mechanically inferior fibrocartilagenous tissue.
Another surgical technique is mosaicplasty or osteochondral autograft transfer system (OATS). In this case, cylindrical plugs of healthy articular cartilage from a low-load bearing region of the knee are taken and transplanted into the defective region. This technique, however, can result in excessive donor-site morbidity and associated pain. Additionally, surgeons have reported that the gaps between the round transplants are frequently filled with fibrocartilage which can eventually erode away, thus potentially compromising the integrity of repair throughout the affected area.
The only FDA-approved cartilage treatment product in the market involves autologous chondrocyte implantation (CartiCel™). Autologous chondrocyte implantation involves performing an initial biopsy of healthy cartilage from the patient, isolating the cells from the tissue, expanding the cells in vitro by passaging them in culture, and then reintroducing the cells into the defective area. The cells are retained within the defect by applying a periosteal tissue patch over the defect, suturing the edges of the patch to the host tissue, and then sealing with fibrin glue. The efficacy of this expensive procedure, however, has recently been put into question by studies that have shown that only a few of the injected cells are retained within the defect and that they may not significantly contribute to the repair process. The healing observed is similar to that observed with microfracture or abrasion of the bone bed, suggesting that it is the preparation of the bone bed and not the introduction of the cells that facilitates the healing process.
Tissue engineering strategies for healing cartilage are being investigated by several academic and commercial teams and show some promise. One approach primarily involves using a carrier or a scaffold to deliver cells or stimulants to the defect site. The scaffold material can be a purified biologic polymer in the form of a porous scaffold or a gel (purified collagens, glycoproteins, proteoglycans, polysaccharides, or the like in various combinations) or porous scaffolds of synthetic biodegradable polymers (PLA, PGA, PDO, PCL, or the like, in various combinations). Several challenges remain with this approach, however. Some of these challenges include retention of the active stimulant at the defect site, inability to control the rate of release of the stimulant (resulting in tissue necrosis due to overdose), and cytotoxicity of the cells due to the degradation by-products of the synthetic polymers.
In another technique, various collagen scaffolds have been used to provide a scaffold for repair and regeneration of damaged cartilage tissue. U.S. Pat. No. 6,042,610 to ReGen Biologics, hereby incorporated by reference, discloses the use of a device to regenerate meniscal fibrocartilage. The disclosed device comprises a bioabsorbable material made at least in part from purified collagen and glycosaminoglycans (GAG). Purified collagen and glycosaminoglycans are colyophilized to create a foam and then cross-linked to form the device. The device can be used to provide augmentation for a damaged meniscus. Related U.S. Pat. Nos. 5,735,903, 5,479,033, 5,306,311, 5,007,934, and 4,880,429 also disclose a meniscal augmentation device for establishing a scaffold adapted for ingrowth of meniscal fibrochondrocyts.
It is also known to use naturally occurring extracellular matrices (ECMs) to provide a scaffold for tissue repair and regeneration. One such ECM is small intestine submucosa (SIS). SIS has been described as a natural biomaterial used to repair, support, and stabilize a wide variety of anatomical defects and traumatic injuries. See, for example, Cook® Online New Release provided by Cook Biotech at “www.cookgroup.com”. The SIS material is reported to be a naturally-occurring collageneous matrix derived from porcine small intestinal submucosa that models the qualities of its host when implanted in human soft tissues. Further, it is taught that the SIS material provides a natural matrix with a three-dimensional structure and biochemical composition that attracts host cells and supports tissue remodeling. SIS products, such as Oasis material and Surgisis material, are commercially available from Cook Biotech, Bloomington, Ind.
An SIS product referred to as RESTORE Orthobiologic Implant is available from DePuy Orthopaedics, Inc. in Warsaw, Indiana. The DePuy product is described for use during rotator cuff surgery, and is provided as a resorbable framework that allows the rotator cuff tendon to regenerate itself. The RESTORE Implant is derived from porcine small intestine submucosa that has been cleaned, disinfected, and sterilized. Small intestine submucosa (SIS) has been described as a naturally-occurring ECM composed primarily of collagenous proteins. Other biological molecules, such as growth factors, glycosaminoglycans, etc., have also been identified in SIS. See Hodde et al., Tissue Eng. 2(3): 209-217 (1996); Voytik-Harbin et al., J. Cell Biochem., 67:478-491 (1997); McPherson and Badylak, Tissue Eng., 4(1): 75-83 (1998); Hodde et al., Endothelium, 8(1):11-24 (2001); Hodde and Hiles, Wounds, 13(5): 195-201 (2001); Hurst and Bonner, J. Biomater. Sci. Polym. Ed., 12(11) 1267-1279 (2001); Hodde et al., Biomaterial, 23(8): 1841-1848 (2002); and Hodde, Tissue Eng., 8(2): 295-308 (2002), all of which are incorporated by reference herein. During seven years of preclinical testing in animals, there were no incidences of infection transmission from the implant to the host, and the SIS material has not decreased the systemic activity of the immune system. See Allman et al., Transplant, 17(11): 1631-1640 (2001); Allman et al., Tissue Eng., 8(1): 53-62 (2002).
Whilesmall intestine submucosa is available, other sources of submucosa are known to be effective for tissue remodeling. These sources include, but are not limited to, stomach, bladder, alimentary, respiratory, or genital submucosa, or liver basement membrane. See, e.g., U.S. Pat. Nos. 6,171,344, 6,099,567, and 5,554,389, hereby incorporated by reference. Further, while SIS is most often porcine derived, it is known that these various submucosa materials may be derived from non-porcine sources, including bovine and ovine sources. Additionally, other collageneous matrices are known, for example lamina propria and stratum compactum.
For the purposes of this invention, it is within the definition of a naturally occurring ECM to clean, delaminate, and/or comminute the ECM, or even to cross-link the collagen fibers within the ECM. It is also within the definition of naturally occurring ECM to fully or partially remove one or more sub-components of the naturally occurring ECM. However, it is not within the definition of a naturally occurring ECM to extract and purify the natural collagen or other components or sub-components of the ECM and reform a matrix material from the purified natural collagen or other components or sub-components of the ECM. Thus, while reference is made to SIS, it is understood that other naturally occurring ECMs are within the scope of this invention. Thus, in this application, the terms “naturally occurring extracellular matrix” or “naturally occurring ECM” are intended to refer to extracellular matrix material that has been cleaned, disinfected, sterilized, and optionally cross-linked. The terms “naturally occurring ECM” and “naturally occurring extracellular matrix” are also intended to include foam material made from naturally occurring ECM as described in U.S. patent application Ser. No. 10/195,354 entitled “Porous Extracellular Matrix Scaffold and Method”, the toughened material made from naturally occurring ECM as described in U.S. patent application Ser. No. 10/195,795 entitled “Meniscus Regeneration Device and Method”, and the hardened material made from naturally occurring ECM as described in U.S. patent application Ser. No. 10/195,719 entitled “Devices from Naturally Occurring Biologically Derived Materials”, all filed concurrently herewith and incorporated by reference.
The following patents, hereby incorporated by reference, disclose the use of ECMs for the regeneration and repair of various tissues: U.S. Pat. Nos. 6,379,710; 6,334,872; 6,187,039; 6,176,880; 6,126,686; 6,099,567; 6,096,347; 5,997,575; 5,993,844; 5,968,096; 5,955,110; 5,922,028; 5,885,619; 5,788,625; 5,733,337; 5,762,966; 5,755,791; 5,753,267; 5,711,969; 5,645,860; 5,641,518; 5,554,389; 5,516,533; 5,460,962; 5,445,833; 5,372,821; 5,352,463; 5,281,422; and 5,275,826.
It is also known to promote cartilage growth using glycosaminoglycans (GAG), such as hyaluronic acid (HA), dermatan sulfate, heparan sulfate, chondroitin sulfates, keratin sulfate, etc. See, e.g., U.S. Pat. Nos. 6,251,876 and 6,288,043, hereby incorporated by reference. GAGs are naturally found mostly in the extracellular matrix and on the cell surface as proteoglycans. These macromolecules are secreted by cells and play a role in both signal transduction and storage of some growth factors. In addition to the biological functions, the viscoelastic properties of GAGs provide a mechanical function by providing lubrication within a joint, to decrease friction. Hyaluronic acid is a natural component of the extracellular matrix of most cartilage tissues. HA is a linear polymer made up of repeating GAG disaccharide units of Dglucuronic acid and N-acetylglycosamine in β(1-3)and β(1-4) linkages. Illustratively HA can have a molecular weight ranging from about 300,000 kDa to about 6,000,000 kDa and can be uncrosslinked, naturally crosslinked, or crosslinked using mechanical, chemical, or enzymatic methods. The effect of treating extrasynovial tendons with HA and chemically modified HA has also been studied with reference to tendon gliding resistance and tendon adhesions to surrounding tissue after repair. Momose, Amadio, Sun, Chunfeng Zhao, Zobitz, Harrington and An, “Surface Modification of Extrasynovial Tendon by Chemically Modified Hyaluronic Acid Coating,” J. Biomed. Mater. Res. 59: 219-224 (2002).